Yarn feeding device

ABSTRACT

The invention relates to a yarn feeding device (F) for weaving or knitting machines whose winding element (W) is driven by an electric motor (M) controlled by an electronic speed control device (CU). According to the invention, the electric motor (M) is a synchronous motor, in particular, a permanent magnet (PM) motor with the speed control device (CU) provided for effecting a permanent vector control with the stator being sinusoidally acted upon. Continuously determined information pertaining to the relevant rotational position of the rotor (R) of the motor (M) is used in the speed control device (CU), which serves to perform permanent vector control, in order to adjust at least one predetermined rotational position (X 1 , X 2 ) of the winding element (W).

FIELD OF THE INVENTION

The invention relates to a yarn feeding device and more specifically tothe use of an electric synchronous motor for controlling a yarn feedingdevice.

BACKGROUND OF THE INVENTION

The yarn feeding device known from EP 0 580 267 A1 comprises apre-control device using the signals of a position sensor provided inthe yarn feeding device in order to slowly drive the electric motorafter switching off the electric motor by the speed control device untilthe winding element reaches a predetermined rotational position inrelation to the housing. The control effort needed is considerable.

The yarn feeding device as known from EP 0 327 973 A (U.S. Pat. No.4,936,356) is provided with a detector fixed to the housing whichdetector can be actuated by a transmitter rotating with the windingelement in order to adjust the winding element with slow rotationalspeed into a predetermined position relative to the housing when thespeed control device has to switch off the electric motor. Thepredetermined position of the winding element may be appropriate inorder to facilitate threading of the yarn through the yarn feedingdevice.

U.S. Pat. No. 4,814,677 A generally discloses a field orientationcontrol system of a permanent magnet motor operating by sinusoidalstator part actuation. The information on the momentary rotary positionof the rotor is derived from measured stator voltages and statorcurrents. This is carried out without additional position sensors. Thedetected relative rotary positions of the rotor are used for the speedcontrol and the torque control of the permanent magnet motor.

The so-called brushless DC motor (BLDC) known from EP 10 52 766 A2 (U.S.Pat. No. 6,356,048) is employed as the drive source for the windingelement of a yarn feeding device. The motor is designed without sensors.A control system is provided for controlling the torque and/or the speedof the motor. The control system calculates the commutation switchingpoints for the stator parts in six angled positions which are distant bya respective 60° without a position sensor. In this case the zerocrossing points of the backwards acting electromotive force aredetermined which are induced in the stator windings by the rotation ofthe rotor magnets. In-between the six switching points, distributedabout a full revolution, the position of the rotor remains unknown. Thebackwards acting electromotive force is effected according to atrapezoidal course. This motor drive control principle does not allow asufficiently accurate position control and position observation of thewinding element because only predetermined rotary positions of the rotorare detected.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a yarn feeding device of thekind as disclosed herein which allows in a structurally simple andcontrollable fashion an accurate position control and/or positionobservation of the winding element in order to selectively and preciselyreproducibly adjust a predetermined rotary position of the windingelement which rotary position is needed for an auxiliary function of theyarn feeding device.

Additionally, this object can be achieved particularly expediently andsimply by employing an electric synchronous motor for the control of theyarn feeding device, particularly a permanent magnet motor, whichoperates with permanent (continuous) stator vector control andsinusoidal stator actuation, in order to carry out the position controland/or position observation of the winding element in relation to thehousing of the yarn feeding device, and to use for that purpose theinformation about the respective rotary position of the rotor whichanyhow is needed for the permanent (continuous) stator vector control.

The speed device equipped with the microprocessor detects permanently(continuously) the relative rotary position of the vector of the rotorwhich position corresponds to the momentary rotary position of therotor. This is carried out to permanently (continuously) rotate thestator vector generated by the sinusoidal actuation of the stator partsuch that the desired speed and/or the desired torque is gainedsubstantially steplessly. The information on the momentary rotaryposition of the rotor or the rotor vector, respectively, is used toadjust the winding element into the at least one predetermined relativeposition in the housing by using the fixed structural correlationbetween the rotor, the shaft and the winding element. This relativeposition is useful to thread the yarn by means of an automatic threadingdevice without further checking the rotary position of the windingelement, or to adjust the winding element into a position in which amanual threading process can be carried out without problems.Additionally or alternatively, the information by which during thepermanent vector control of the rotor rotation is followed can be usedto measure the wound on yarn length. The capacity of the microprocessoris sufficient without problems for this additional function. Nosophisticated additional control circuits are needed, and also no costlysensor assemblies.

The motor, expediently, is a permanent magnet motor which is availablefor fair costs and is efficient and takes up only minimal mountingspace. Basically, however, also other types of synchronous motors may beused within the scope of this invention, like so-called reluctancemotors, so even so-called “switched reluctance motors (SR)”. Inprinciple, even a so-called BLDC (brushless DC motor) could co-operatewith the speed control device according to the invention.

In order to be able to permanently (continuously) and precisely followthe movement of the rotor, it is of advantage when the permanent magnetsin the rotor are designed (e.g. formed), magnetised and/or configured(placed) such that the backward acting electromotive force induced bythe rotor in the stator winding follows a sinusoidal course. With thehelp of the sinusoidal course the respective rotor rotary position canbe calculated accurately which is of advantage for the permanent(continuous) vector control, and which is very suitable as a sideproduct also for the position control and/or position observation of thewinding element relative to the housing.

A calculating circuit is, expediently, contained in the speed controldevice, preferably in a microprocessor, which calculates the relativerotor rotary position with the help of the induced backwards orientedelectromotive force. The electromotive force can be measured preciselyin terms of its course and its magnitude.

Additionally, if expedient, at least one rotary position sensor may beprovided and connected to the speed control device. The signal of thissensor may be used in order to build up a holding torque by means of themotor control and to retain the winding element at the predeterminedrotary position relative to the housing despite an externally actingrotary force, and in order to retrieve the rotary position of thewinding element or the rotor, respectively, during a restart of themotor.

Expediently, several relative rotary positions of the winding elementwithin a 360° rotation of the winding element are programmed and can beselectively adjusted for correspondingly control stopping of the motor.That means that the winding element as well is stopped in the mostsuitable rotary position depending on the planned auxiliary function atthe yarn feeding device. This relative rotary position can be selectedcompletely arbitrarily.

It is expedient to place the stator part in a predetermined rotaryposition in the housing. By this measure each desired relative positionof the winding element, as programmed, can be set in relation to thehousing already during assembly of the yarn feeding device, without thenecessity to carry out further programming.

By means of the determined permanent relative rotary position of therotor during the vector control even the rotary travel of the windingelement at least from the start to the end of a driving period can bemeasured without additional equipment parts, which is useful toprecisely measure the wound on yarn length.

Alternatively, the yarn length may be measured in the same fashion evenbetween selected points in time or selected different relative rotarypositions of the rotor, respectively, by evaluating the informationabout the momentary rotor rotation angle for this additional function.

A predetermined relative rotary position of the winding element inrelation to the housing may be a full yarn threading position in whichan exit opening of the winding element is aligned with a threading pathprovided in the housing of the yarn feeding device. The on-boardpneumatic threading device then may thread a new yarn without furtherinterference by an operator.

Alternatively, the predetermined rotary position of the winding elementin relation to the housing and adjustment by means of the vector controlmay be a semi-threading position in which an exit opening of the windingelement is positioned outside of shielding housing parts such that noobstacles hinder the manual gripping of the yarn for knotting the yarnto yarn material already provided on the storage surface, or such thatthe winding element does not have to be rotated manually into a positionbeneficial to this auxiliary function.

An electronic yarn length measuring device can be supplied with theinformation on the rotor rotary positions during the vector control inorder to derive precise information on the yarn consumption.

In the case that additionally a position sensor for the winding elementis provided in the yarn feeding device, in order to signal at least oneposition or to confirm a position, respectively, then this positionsensor may be used for generating an aligning holding torque by means ofthe motor and in co-action with the speed control device. The holdingtorque retains the winding elements in the adjusted rotor position evenif external forces tend to further rotate the winding element. The motorcontrol is apt to adapt automatically to the magnitude of the actingexternal force in order to hold the winding element stationary.

Expediently, the position sensor comprises permanent magnets distributedalong the circumference of the winding element, and at least onedetecting element fixed to the housing which responds to the passage ofeach permanent magnet. Preferably, a digitally operating Hall element isprovided generating a digital signal whenever a permanent magnet ispassing. However, particularly expedient is also an analog Hall sensorresponding respectively to one pair of adjacent permanent magnets inorder to precisely monitor even rotation ranges of the winding element.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will be explained with reference to thedrawings wherein:

FIG. 1 is a longitudinal section of a yarn feeding device comprising asynchronous electric motor of a permanent magnet type as a drivingsource for a winding element, and

FIG. 2 is a cross-section of the yarn feeding device.

DETAILED DESCRIPTION

A yarn feeding device F as shown in FIG. 1 and FIG. 2 is a weft yarnfeeding device for a weaving machine (not shown). However, the inventioncan be applied to a yarn feeding device for a knitting machine (notshown) as well, the yarn feeding device then having a rotary yarnstorage drum defining a winding element.

The yarn feeding device F in FIGS. 1 and 2 comprises a housing 1 with ahousing bracket 2 containing additional components. A hollow shaft 3 isrotatably supported in a bearing 4 in the housing 1. The shaft 3stationarily supports by its free end a storage drum D which ispositioned below the housing bracket 2. In order to prevent that thestorage drum D from rotating together with the shaft 3 permanent magnets12 are provided in the housing which magnetically co-act with not shownpermanent magnets placed in the storage drum D.

A rotor R is provided on the shaft 3. The rotor co-acts with stator partS stationarily placed in the housing. The stator S is fixed by apositioning means 13 (FIGS. 1 and 2) in a predetermined rotary position.

An electric motor control device CU containing a microprocessor MP iscontained in the housing bracket 2. The motor control device CU isconnected for signal transmission to a yarn sensor assembly 8 andcontrols the speed, the torque and the rest periods of the electricmotor M depending on the size of a yarn store formed by yarn windings onthe storage drum D. Furthermore, a yarn threading path 9 is provided inthe housing bracket 2 for co-action with a not shown, on-board pneumaticthreading device in order to thread a new yarn entirely through the yarnfeeding device. Furthermore, a withdrawal opening 7 for the yarn isplaced at the housing bracket 2.

A winding element W having an exit opening 6 is fixed to the shaft 3.The relative rotary position of the exit opening with respect to therotor R is structurally fixed. The winding element W may be formed as afunnel-shaped disk 10 containing a not shown winding tube terminating atthe exit opening 6. At the winding element W permanent magnets 11 may beprovided which are distributed along the circumference and which co-actwith a detecting element H (for example, a digital or analog Hallsensor) stationarily provided in the housing bracket 2.

The electric motor M is an electric synchronous motor, preferably apermanent magnet motor (a so-called PM-motor). FIG. 2 illustrates thegeometric distribution of permanent magnets PM in the rotor R and aschematic view of the stator part S (without stator windings providedtherein).

With the help of the speed control device CU and the microprocessor MP apermanent vector control of the motor M is carried out, i.e., the rotaryposition of the rotor vector is determined continuously without sensors,and the stator vector is rotated by a corresponding current actuationcontinuously such that the desired speed and an optimum development ofthe torque result. The actuation of the stator windings is carried outsinusoidally. The permanent magnets PM in the rotor R are designed(formed), magnetised and/or configured (placed) such that, furthermore,forced by the function, the backwards oriented electromotive force inthe stator windings resulting from the rotation of the rotor R inrelation to the stator parts S will be induced with a sinusoidal course.With the help of the sinusoidal course of the induced electromotiveforce the rotary position of the rotor vector is continuouslydetermined. The stator vector is rotated according to the determinationby actuation of the stator part. The information about the momentaryrotary position of the rotor vector or the rotor, respectively, inrelation to the stator windings or the stator part S, respectively, andthe housing, furthermore is used for the position control and/or theposition observation of the winding element W.

Referring to FIG. 2 a predetermined rotary position X1 of the windingelement W is a so-called full threading position in relation to thehousing 1. In this full threading position the exit opening 6 of thewinding element W is precisely aligned with the threading path 9structurally integrated into the housing bracket 2. In thispredetermined rotary position X1 the yarn while blown through the shaft3 and out of the exit opening 6 is guided along the threading path 9 andfinally is brought into the exit opening 7 without manual interference.However, a prerequisite for this function is that the winding element isstopped precisely at the predetermined rotary position X1 when theelectric motor M is stopped. For adjusting this rotary position X1 nowthe permanently (continuously) present information on the rotaryposition of the rotor R in relation to the stator parts S or thehousing, respectively, is used to precisely stop the winding element Wat the predetermined rotary position X1 by means of the speed controldevice CU, which is useful in the event of a yarn breakage, as detectedby not shown detectors.

In FIG. 2, furthermore, a further predetermined rotary position X2 isshown for the exit opening 6 of the winding element W. The rotaryposition X2 is predetermined such that the exit opening 6 is stoppedoffset by 90° in relation to the housing bracket 2, i.e. that the exitopening is not covered by any housing components hindering directaccess.

In case that a not shown yarn detector detects a yarn breakage situationwhile yarn material is still present on the storage surface of thestorage drum D, the winding element will be stopped in the rotaryposition X2 by means of the vector control of the electric motor M suchthat the then activated pneumatic threading device will present theblown-through yarn at an easily accessible position of the housing forbeing gripped by the operator. By a corresponding re-correlation of thesignal generated by the yarn detectors the speed control device CU willhave been informed beforehand in which of the two predeterminedpositions X1, X2 the yarn winding element W has to be adjusted for acertain operating condition.

The rotary position sensor H does not need to be used for this task.However, this sensor may assist in preventing undesired rotation of thewinding element W when stopped at the respective position X1 or X2,respectively. This means that then the speed control device CU willbuild a holding torque in the one or the other sense of rotation inorder to locally retain the winding element despite the influence ofexternal forces (the yarn tension or the like). Furthermore, the rotaryposition sensor H may be used for determining the rotary position of therotor R and at the same time of the winding element W in case of a newoperation start-up and as rapidly as possible.

Furthermore, a yarn length measuring device can be interlinked with thespeed control device CU in order to measure the length of the wound onyarn by means of the rotary travel Y of the winding element W.

The respective predetermined rotary position X1, X2 may be selected andadjusted arbitrarily, because the control permanently follows themovement of the rotor during operation of the motor and since therespective position information is present continuously. This means thatneither the rotary positions X1, X2, nor further rotary positions of thewinding element W as needed for other purposes have to be fixedbeforehand either by the geometric relations between the stator S andthe rotor R or by the geometric placement of the position sensor H. Tothe contrary any rotary positions can be freely adjusted or programmed,respectively, as they are best for the auxiliary functions of the yarnfeeding device, e.g. for threading processes. The predetermined positionX2 may be varied later by corresponding reprogramming, which is usefulin a situation such as where several yarn feeding devices have to beplaced close to each other at a weaving machine such that they mightblock the respective access to the position X2 in FIG. 2. In such a casethe position X2 can be put to another location where comfortable accessis possible for the operator despite the restriction by the severalclosely arranged yarn feeding devices.

Although a particular preferred embodiment of the invention has beendisclosed in detail for illustrative purposes, it will be recognizedthat variations or modifications of the disclosed apparatus, includingthe rearrangement of parts, lie within the scope of the presentinvention.

1. Yarn feeding device for weaving machines or knitting machines, theyarn feeding device comprising a housing in which a shaft provided witha winding element is rotatably supported, a storage surface for yarnwindings formed by the winding element, sensor assemblies at least forscanning the yarn windings, an electric motor consisting of a statorpart and a rotor which is connected to the shaft for rotating thewinding element, and an electronic speed control device of the electricmotor which electronic speed control device is connected for signaltransmissions with the sensor assemblies and the electric motor, and aposition control and position observation at least for adjusting thewinding element by the electric motor into at least one predeterminedrotary stop position in relation to the housing, wherein the electricmotor is a synchronous motor controlled by the speed control device, thespeed control device having a microprocessor for a permanent vectorcontrol of the electric motor by detecting the relative rotary positionof a vector of the rotor to determine the relative rotary rotor positionand by rotating a stator vector in relation to the detected vector ofthe rotor by sinusoidal stator actuation, and wherein the predeterminedrotary stop position of the winding element is adjusted by stopping theelectric motor by use of the permanently determined vector controlinformation in the speed control device.
 2. Yarn feeding device as inclaim 1, wherein the electric motor is a permanent magnet motorcontaining magnetized and structured permanent magnets distributed inthe rotor according to a predetermined geometry, and wherein thedistribution, structure and magnetization of the permanent magnets areselected such that a sinusoidal course of backwards acting electromotiveforce is induced in the stator part by the relative rotor rotation. 3.Yarn feeding device as in claim 2, wherein the electric motor is asensor-free permanent magnet motor, and wherein a calculation circuit isprovided in the speed control device for permanently calculating therelative rotor rotary position with the help of indirect measurements ofthe induced electromotive force.
 4. Yarn feeding device as in claim 1,wherein at least one rotary position sensor is provided in the yarnfeeding device for detecting a predetermined rotary stop position eitherof the rotor or of the winding element, and wherein the rotary stopsensor is connected to the speed control device.
 5. Yarn feeding deviceas in claim 4, wherein the rotary position sensor comprises permanentmagnets distributed along the circumference of the winding element andat least one Hall sensor detection element fixed to the housing, whichdetection element either responds digitally to the passage of eachpermanent magnet or has an analog response to the relative rotaryposition of a respective pair of permanent magnets.
 6. Yarn feedingdevice as in claim 1, wherein a plurality of predetermined relativerotary positions of the winding element is programmed within a 360°rotation in the speed control device.
 7. Yarn feeding device as in claim1, wherein a yarn length measuring device is interlinked with the speedcontrol device for permanently transmitting information on the relativerotary position to the yarn length measuring device for measuring bymeans of the information on the relative rotary position of the rotorthe rotation travel of the winding element representing a wound on yarnlength on the storage surface either as fed between the start and theend of the driving period or between selected points in time or selecteddifferent relative rotary positions of the rotor.
 8. Yarn feeding deviceas in claim 1, wherein one predetermined rotary stop position of thewinding element is a relative rotor rotary position in which an exitopening of the winding element connected to the rotor is aligned with athreading path positioned in a stationary position in the housing of theyarn feeding device.
 9. Yarn feeding device as in claim 1, wherein onepredetermined rotary stop position of the winding element is a rotorrotary position where an exit opening of the winding element is stoppedin relation to the housing in a semi-threading position where the exitopening is positioned at the side of housing parts obstructing a manualaccess from the outside to the exit opening.
 10. A method of operating ayarn feeding device for weaving machines or knitting machines, the yarnfeeding device having a winding element defining a storage surface foryarn windings and being disposed on a shaft that is rotatably supportedin a housing, a sensor assembly adapted to scan the yarn windings, asynchronous electric motor with a stator fixed with respect to thehousing and a rotor connected to the shaft for rotating the windingelement, and an electronic speed control device connected for signaltransmissions with the sensor assembly and the electric motor andadapted to monitor rotary position of the shaft and control the speed ofthe electric motor, the method comprising: detecting a relative rotaryposition of a vector of the rotor to determine the rotary rotor positionrelative to the stator; rotating a stator vector in relation to thedetected vector of the rotor by sinusoidal stator actuation; controllingthe speed of the electric motor through continuous vector control of theelectric motor; and stopping rotation of the shaft by controlling theelectric motor to position the winding element in a predetermined rotarystop position in relation to the housing by use of the permanentlydetermined vector control information in the speed control device. 11.The method of operating a yarn feeding device of claim 10, includingdetermining the relative rotary rotor position by calculation based uponindirect measurements of induced electromotive force in the stator. 12.The method of operating a yarn feeding device of claim 10, includingpermanently transmitting information on the relative rotary rotorposition to a yarn length measuring device.
 13. A yarn feeding devicecomprising: a winding element defining a storage surface for yarnwindings and being rotatably supported in a housing; a sensor assemblyadapted to scan the yarn windings; a synchronous electric motor with astator fixed with respect to the housing and a rotor connected to rotatetogether with the winding element; and an electronic speed controldevice connected for signal transmissions with the sensor assembly andthe electric motor and adapted to monitor the rotary position of thewinding element and control the rotational speed of the electric motor,the electronic speed control device being adapted to detect a relativerotary position of a vector of the rotor to determine the relativerotary rotor position, rotate a stator vector in relation to thedetected vector of the rotor by sinusoidal stator actuation, controlrotational speed of the electric motor through continuous vector controlof the electric motor, and stop rotation of the winding element at apredetermined rotary stop position in relation to the housing bycontrolling the electric motor by use of the continuously determinedvector control information.
 14. The yarn feeding device of claim 13,wherein the electric motor is sensor-free, and wherein the speed controldevice comprises a microprocessor adapted to calculate the relativerotor rotary position based upon indirect measurements of inducedelectromotive force in the stator.
 15. The yarn feeding device of claim13, wherein a threading path is positioned in a stationary position inthe housing, an exit opening is disposed in the winding element, and thepredetermined rotary stop position of the winding element corresponds toa relative rotor rotary position at which the exit opening of thewinding element is aligned with the threading path.
 16. The yarn feedingdevice of claim 13, wherein an exit opening is disposed in the windingelement, and the predetermined rotary stop position of the windingelement corresponds to a relative rotor rotary position at which theexit opening of the winding element is disposed in relation to thehousing in a semi-threading position wherein the exit opening ispositioned to the side of housing parts obstructing manual access fromthe outside to the exit opening.